U.S. patent number 5,155,461 [Application Number 07/653,347] was granted by the patent office on 1992-10-13 for solenoid stator assembly for electronically actuated fuel injectors and method of manufacturing same.
This patent grant is currently assigned to Diesel Technology Corporation. Invention is credited to Leland Haines, Robert D. Straub, Richard F. Teerman, Roger L. Wolfsen.
United States Patent |
5,155,461 |
Teerman , et al. |
October 13, 1992 |
Solenoid stator assembly for electronically actuated fuel injectors
and method of manufacturing same
Abstract
A solenoid stator assembly for electronically actuated fuel
injectors is disclosed as having an E-shaped stator core including
a top portion and three parallel pole pieces extending orthogonally
therefrom. The outer pole pieces each have an outermost side, and
each of the three pole pieces has a distal end, a face being formed
across the distal end. Each of the outer pole pieces has an
attachment slot formed across its outermost side proximate its
distal end. A coil of electric wire is disposed around an
insulating spool disposed on the central pole piece, and leads from
the coil are connected to terminals. A flange on one end of the
spool exerts outward forces on the outer pole pieces, prestressing
them to resist further flexing caused by outwardly directed forces
applied by errant fuel under pressure. An insulating cover is
molded around the solenoid stator assembly, enveloping it except
for portions of the terminals and the faces of the pole pieces, the
cover being bonded to at least the stator core. The cover is molded
into the attachment slots in the outer pole pieces to enhance
adherence of the cover material to the stator core and provide a
barrier to any tendency of errant fuel attempting to traverse the
interface between the insulating cover and outermost side of each
outer pole piece.
Inventors: |
Teerman; Richard F. (Wyoming,
MI), Straub; Robert D. (Lowell, MI), Wolfsen; Roger
L. (Coopersville, MI), Haines; Leland (Northville,
MI) |
Assignee: |
Diesel Technology Corporation
(Grand Rapids, MI)
|
Family
ID: |
24620481 |
Appl.
No.: |
07/653,347 |
Filed: |
February 8, 1991 |
Current U.S.
Class: |
335/260;
29/602.1; 335/278; 336/96 |
Current CPC
Class: |
F02M
63/0019 (20130101); H01F 3/02 (20130101); H01F
7/081 (20130101); H01F 41/02 (20130101); F02M
57/023 (20130101); Y10T 29/4902 (20150115) |
Current International
Class: |
H01F
41/02 (20060101); H01F 3/00 (20060101); H01F
7/08 (20060101); H01F 3/02 (20060101); H01F
003/00 (); H01F 007/08 () |
Field of
Search: |
;335/260,278,281,292,294
;336/96 ;29/602.1 ;264/272.19,272.2 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
4568021 |
February 1986 |
Deckard et al. |
|
Foreign Patent Documents
Primary Examiner: Broome; Harold
Claims
What is claimed is:
1. A solenoid stator assembly for electronically actuated fuel
injectors, the solenoid stator assembly comprising:
a stator core including a top portion having a first end and a
second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, the first and second outer pole pieces each having an
outermost side and a distal end, a face being formed across each
distal end, the first and second outer pole pieces each having an
attachment slot formed across its outermost side proximate its
distal end, the slot being substantially parallel to the top
portion;
a coil of electric wire disposed about any one of the top portion
and pole pieces, the wire having at least first and second ends
extending from the coil to form respective first and second
leads;
first and second terminals electrically connected to the first and
second leads respectively;
electrical insulating means for separating the coil from said one
of the top portion and pole pieces to prevent electrical contact
therebetween; and
an insulating cover bonded to at least the stator core and
substantially enveloping the solenoid stator assembly except for
portions of the first and second terminals and the faces of the
first and second outer pole pieces, the cover being molded into the
attachment slots in the first and second outer pole pieces to
enhance adherence of the cover to the first and second outer pole
pieces.
2. The solenoid stator assembly as defined by claim 1, wherein the
attachment slot formed across each of the outermost sides of the
first and second outer pole pieces proximate their respective
distal ends has a T-shaped cross section.
3. The solenoid stator assembly as defined by claim 1, further
comprising an insulating cap disposed on the stator core proximate
the top portion thereof to receive the first and second terminals
and to maintain the first and second terminals in position while
the insulating cover is being molded around the solenoid stator
assembly.
4. The solenoid stator assembly as defined by claim 3, wherein the
insulating cap is formed of phenolic material.
5. The solenoid stator assembly as defined by claim 1 further
including prestressing means for applying a force proximate the
distal end of the first outer pole piece and a force proximate the
distal end of the second outer pole piece, the forces acting in
generally coincident but opposite directions to bias the first and
second outer pole pieces away from each other.
6. A solenoid stator assembly for, electronically actuated fuel
injectors, the solenoid stator assembly comprising:
an E-shaped stator core including a top portion having a first end
and a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
each having an outermost side and the first and second outer pole
pieces and the central pole piece each having a distal end, a face
being formed across each distal end, the first and second outer
pole pieces each having an attachment slot formed across its
outermost side proximate its distal end, the slot being
substantially parallel to the top portion;
a coil of electric wire disposed about the central pole piece, the
wire having at least first and second ends extending from the coil
to form respective first and second leads;
first and second terminals electrically connected to the first and
second leads respectively;
electrical insulating means for separating the coil from the
central pole piece to prevent electrical contact therebetween;
and
an insulating cover bonded to at least the stator core and
substantially enveloping the solenoid stator assembly except for
portions of the first and second terminals and the faces of the
first and second outer pole pieces and of the central pole piece,
the cover being molded into the attachment slots in the first and
second outer pole pieces to enhance adherence of the cover to the
first and second outer pole pieces.
7. The solenoid stator assembly as defined by claim 6, wherein the
attachment slot formed across each of the outermost sides of the
first and second outer pole pieces proximate their respective
distal ends has a T-shaped cross section.
8. The solenoid stator assembly as defined by claim 6, wherein the
electrical insulating means for separating the coil from the
central pole piece includes a spool disposed around the central
pole piece and between the central pole piece and the coil of
electric wire.
9. The solenoid stator assembly as defined by claim 8, wherein the
coil has a first end and a second end, the first lead extending
from the first end of the coil, the second lead extending from the
second end of the coil, between the coil and the spool, to the
first end of the coil, the second lead being held in position
against the spool by the coil without requiring additional
security.
10. The solenoid stator assembly as defined by claim 8, wherein the
spool is formed of phenolic material.
11. The solenoid stator assembly as defined by claim 6, wherein the
insulating cover is molded in situ of phenolic material.
12. The solenoid stator assembly as defined by claim 6, further
comprising an insulating cap disposed on the stator core proximate
the top portion thereof to receive the first and second terminals
and to maintain the first and second terminals in position while
the insulating cover is being molded around the solenoid stator
assembly.
13. The solenoid stator assembly as defined by claim 12, wherein
the insulating cap is formed of phenolic material.
14. A solenoid stator assembly for electronically actuated fuel
injectors, the solenoid stator assembly comprising:
an E-shaped stator core including a top portion having a first end
and a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
and the central pole piece each having a distal end, a face being
formed across each distal end;
a coil of electric wire disposed around the central pole piece, the
wire having at least first and second ends extending from the coil
to form respective first and second leads;
first and second terminals electrically connected to the first and
second leads respectively;
electrical insulating means for separating the coil from the
central pole piece to prevent electrical contact therebetween;
prestressing means for applying a force proximate the distal end of
the first outer pole piece and a force proximate the distal end of
the second outer pole piece, the forces acting in generally
coincident but opposite directions to bias the first and second
outer pole pieces away from each other; and
an insulating cover bonded to at least the stator core and
substantially enveloping the solenoid stator assembly except for
portions of the first and second terminals and the faces of the
first and second outer pole pieces and of the central pole
piece.
15. The solenoid stator assembly as defined by claim 14, wherein
the electrical insulating means for separating the coil from the
central pole piece includes a spool disposed around the central
pole piece and between the central pole piece and the coil of
electric wire.
16. The solenoid stator assembly as defined by claim 15, wherein
the coil has a first end and a second end, the first lead extending
from the first end of the coil, the second lead extending from the
second end of the coil, between the coil and the spool, to the
first end of the coil, the second lead being held in position
against the spool by the coil without requiring additional
security.
17. The solenoid stator assembly as defined by claim 15, wherein
the spool is formed of phenolic material.
18. The solenoid stator assembly as defined by claim 14, wherein
the insulating cover is molded in situ of phenolic material.
19. The solenoid stator assembly as defined by claim 14, further
comprising an insulating cap disposed on the stator core proximate
the top portion thereof to receive the first and second terminals
and to maintain the first and second terminals in position while
the insulating cover is being molded around the solenoid stator
assembly.
20. The solenoid stator assembly as defined by claim 19, wherein
the insulating cap is formed of phenolic material.
21. The solenoid stator assembly as defined by claim 14, wherein
the prestressing means comprises:
a first wedging member disposed between the first outer pole piece
and the central pole piece proximate their respective distal ends;
and
a second wedging member disposed between the second outer pole
piece and the central pole piece proximate their respective distal
ends,
the first and second wedging members having dimensions that exceed,
by specific amounts, respective distances between the first and
second outer pole pieces and the central pole piece when the first
and second outer pole pieces are unbiased, and
the first and second wedging members being inserted into their
respective positions to apply a force proximate the distal end of
the first outer pole piece and a force proximate the distal end of
the second outer pole piece, the forces acting in generally
coincident but opposite directions to bias the first and second
outer pole pieces away from the central pole piece and prestress
the first and second outer pole pieces with restorative forces to
oppose additional, parallel forces applied to the first and second
outer pole pieces and inhibit additional displacement caused
thereby.
22. The solenoid stator assembly of claim 14, wherein the
prestressing means applies a force in a range of 250 to 750 pounds
(1100 to 3350 Newtons) to the first and second outer pole
pieces.
23. A solenoid stator assembly for electronically actuated fuel
injectors, the solenoid stator assembly comprising:
an E-shaped stator core including a top portion having a first end
and a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
each having an outermost side and the first and second outer pole
pieces and the central pole piece each having a distal end, a face
being formed across each distal end, the first and second outer
pole pieces each having an attachment slot formed across its
outermost side proximate its distal end, the slot being
substantially parallel to the top portion;
a coil of electric wire disposed around the central pole piece, the
wire having at least first and second ends extending from the coil
to form respective first and second leads;
first and second terminals electrically connected to the first and
second leads respectively;
electrical insulating means for separating the coil from the
central pole piece to prevent electrical contact therebetween;
prestressing means for applying a force proximate the distal end of
the first outer pole piece and a force proximate the distal end of
the second outer pole piece, the forces acting in generally
coincident but opposite directions to bias the first and second
outer pole pieces away from each other; and
an insulating cover bonded to at least the stator core and
substantially enveloping the solenoid stator assembly except for
portions of the first and second terminals and the faces of the
first and second outer pole pieces and of the central pole piece,
the cover being molded into the attachment slots in the first and
second outer pole pieces to enhance adherence of the cover to the
first and second outer pole pieces.
24. The solenoid stator assembly as defined by claim 23, wherein
the attachment slot formed across each of the outermost sides of
the first and second outer pole pieces proximate their respective
distal ends has a T-shaped cross section.
25. The solenoid stator assembly as defined by claim 23, wherein
the electrical insulating means for separating the coil from the
central pole piece includes a spool disposed around the central
pole piece and between the central pole piece and the coil of
electric wire.
26. The solenoid stator assembly as defined by claim 25, wherein
the coil has a first end and a second end, the first lead extending
from the first end of the coil, the second lead extending from the
second end of the coil, between the coil and the spool, to the
first end of the coil, the second lead being held in position
against the spool by the coil without requiring additional
security.
27. The solenoid stator assembly as defined by claim 25, wherein
the spool is formed of phenolic material.
28. The solenoid stator assembly as defined by claim 23, wherein
the insulating cover is molded in situ of phenolic material.
29. The solenoid stator assembly as defined by claim 23, further
comprising an insulating cap disposed on the stator core proximate
the top portion thereof to receive the first and second terminals
and to maintain the first and second terminals in position while
the insulating cover is being molded around the solenoid stator
assembly.
30. The solenoid stator assembly as defined by claim 29, wherein
the insulating cap is formed of phenolic material.
31. The solenoid stator assembly as defined by claim 23, wherein
the prestressing means comprises:
a first wedging member disposed between the first outer pole piece
and the central pole piece proximate their respective distal ends;
and
a second wedging member disposed between the second outer pole
piece and the central pole piece proximate their respective distal
ends,
the first and second wedging members having dimensions that exceed,
by specific amounts, respective distances between the first and
second outer pole pieces and the central pole piece when the first
and second outer pole pieces are unbiased, and
the first and second wedging members being inserted into their
respective positions to apply a force proximate the distal end of
the first outer pole piece and a force proximate the distal end of
the second outer pole piece, the forces acting in generally
coincident but opposite directions to bias the first and second
outer pole pieces away from the central pole piece and prestress
the first and second outer pole pieces with restorative forces to
oppose additional, parallel forces applied to the first and second
outer pole pieces and inhibit additional displacement caused
thereby.
32. The solenoid stator assembly of claim 23, wherein the
prestressing means applies a force in a range of 250 to 750 pounds
(1100 to 3350 Newtons) to the first and second outer pole
pieces.
33. A solenoid stator assembly for electronically actuated fuel
injectors, the solenoid stator assembly comprising:
an E-shaped stator core including a top portion having a first end
and a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
and the central pole piece each having a distal end, a face being
formed across each distal end;
a coil of electric wire disposed around the central pole piece, the
wire having at least first and second ends extending from the coil
to form respective first and second leads;
first and second terminals electrically connected to the first and
second leads respectively;
an electrically insulating spool disposed around the central pole
piece and between the central pole piece and the coil of electric
wire to prevent electrical contact therebetween,
the spool having an end flange that extends from the first outer
pole piece to the second outer pole piece proximate their
respective distal ends,
the portion of the end flange disposed between the first and second
outer pole pieces having a dimension that exceeds, by a specific
amount, the distance between the first and second outer pole pieces
when the first and second outer pole pieces are unbiased, and
the end flange being inserted into position to apply a force
proximate the distal end of the first outer pole piece and a force
proximate the distal end of the second outer pole piece, the forces
acting in generally coincident but opposite directions to bias the
first and second outer pole pieces away from the central pole piece
and prestress the first and second outer pole pieces with
restorative forces to oppose additional, parallel forces applied to
the first and second outer pole pieces and inhibit additional
displacement caused thereby; and
an insulating cover bonded to at least the stator core and
substantially enveloping the solenoid stator assembly except for
portions of the first and second terminals and the faces of the
first and second outer pole pieces and of the central pole
piece.
34. The solenoid stator assembly of claim 33, wherein each of the
faces of the first and second outer pole pieces has a locating
ridge extending along a margin adjacent to the central pole piece
to facilitate positioning the stator core in a mold, the locating
ridge having an edge adjacent to the central pole piece, the edge
being chamfered to facilitate inserting the end flange of the spool
between the first and second outer pole pieces, the locating ridge
being removed during the process of completing the solenoid stator
assembly.
35. A solenoid stator assembly for electronically actuated fuel
injectors, the solenoid stator assembly comprising:
an E-shaped stator core including a top portion having a first end
and a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
each having an outermost side and the first and second outer pole
pieces and the central pole piece each having a distal end, a face
being formed across each distal end, the first and second outer
pole pieces each having an attachment slot formed across its
outermost side proximate its distal end, the slot being
substantially parallel to the top portion;
a coil of electric wire disposed around the central pole piece, the
wire having at least first and second ends extending from the coil
to form respective first and second leads;
first and second terminals electrically connected to the first and
second leads respectively;
an electrically insulating spool disposed around the central pole
piece and between the central pole piece and the coil of electric
wire to prevent electrical contact therebetween,
the spool having an end flange that extends from the first outer
pole piece to the second outer pole piece proximate their
respective distal ends,
the portion of the end flange disposed between the first and second
outer pole pieces having a dimension that exceeds, by a specific
amount, the distance between the first and second outer pole pieces
when the first and second outer pole pieces are unbiased, and
the end flange being inserted into position to apply a force
proximate the distal end of the first outer pole piece and a force
proximate the distal end of the second outer pole piece, the forces
acting in generally coincident but opposite directions to bias the
first and second outer pole pieces away from the central pole piece
and prestress the first and second outer pole pieces with
restorative forces to oppose additional, parallel forces applied to
the first and second outer pole pieces and inhibit additional
displacement caused thereby; and
an insulating cover bonded to at least the stator core and
substantially enveloping the solenoid stator assembly except for
portions of the first and second terminals and the faces of the
first and second outer pole pieces and of the central pole piece,
the cover being molded into the attachment slots in the first and
second outer pole pieces to enhance adherence of the cover to the
first and second outer pole pieces.
36. The solenoid stator assembly of claim 35, wherein each of the
faces of the first and second outer pole pieces has a locating
ridge extending along a margin adjacent to the central pole piece
to facilitate positioning the stator core in a mold, the locating
ridge having an edge adjacent to the central pole piece, the edge
being chamfered to facilitate inserting the end flange of the spool
between the first and second outer pole pieces, the locating ridge
being removed during the process of completing the solenoid stator
assembly.
37. A method for producing a solenoid stator assembly having a
stator core including a top portion having a first end and a second
end, a first outer pole piece extending substantially orthogonally
from the first end of the top portion, a second outer pole piece
extending from the second end of the top portion in a direction
substantially parallel to that of the first outer pole piece, the
first and second outer pole pieces each having an outermost side
and a distal end, a face being formed across the distal end, the
first and second outer pole pieces each having an attachment slot
formed across its outermost side proximate its distal end, the slot
being substantially parallel to the top portion, the method
comprising the steps of:
(a) disposing a coil of electric wire around an insulating
spool;
(b) disposing the insulating spool and coil of wire about at least
one of the pole pieces and the top portion;
(c) applying a permanent spreading force to the first and second
outer pole pieces to prestress them;
(d) connecting the coil across at least two terminals; and
(e) molding an insulating cover that bonds to at least the stator
core and that substantially envelopes the solenoid stator assembly
except for portions of the terminals and the faces of the first and
second outer pole pieces.
38. The method as defined by claim 37, wherein the spreading force
applied to the first and second outer pole pieces is in a range of
250 to 750 pounds (1100 to 3350 Newtons).
39. The method as defined by claim 37, wherein the insulating cover
is molded in situ of phenolic material.
40. The method as defined by claim 37, wherein the spool is formed
of phenolic material.
41. The method as defined by claim 37, wherein the attachment slot
formed across each of the outermost sides of the first and second
outer pole pieces proximate their respective distal ends has a
T-shaped cross section.
42. The method as defined by claim 37, wherein the coil of wire
disposed around the insulating spool has a first end and a second
end, a first lead extending from the first end of the coil, a
second lead being routed from the second end of the coil, between
the coil and the spool, to emerge at the first end of the coil, the
second lead being held in position against the spool by the coil
without requiring additional security.
43. The method as defined by claim 37, further comprising the step
of disposing an insulating cap on the stator pole proximate the top
portion thereof to receive the at least two terminals, thereby
maintaining the terminals in position while the insulating cover is
being molded around the solenoid stator assembly.
44. The method as defined by claim 43, wherein the insulating cap
is formed of phenolic material.
45. A method for producing a solenoid stator assembly having an
E-shaped stator core including a top portion having a first end and
a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
each having an outermost side and the first and second outer pole
pieces and the central pole piece each having a distal end, a face
being formed across the distal end, the first and second outer pole
pieces each having an attachment slot formed across its outermost
side proximate its distal end, the slot being substantially
parallel to the top portion, the method comprising the steps
of:
(a) disposing a coil of electric wire around an insulating
spool;
(b) disposing the insulating spool and coil of wire about the
central pole piece;
(c) applying a permanent spreading force to the first and second
outer pole pieces to prestress them;
(d) connecting the coil across at least two terminals; and
(e) molding an insulating cover that bonds to at least the stator
core and that substantially envelopes the solenoid stator assembly
except for portions of the terminals and the faces of the first and
second outer pole pieces and of the central pole piece.
46. The method as defined by claim 45, wherein the spreading force
applied to the first and second outer pole pieces is in a range of
250 to 750 pounds (1100 to 3350 Newtons).
47. The method as defined by claim 45, wherein the insulating cover
is molded in situ of phenolic material.
48. The method as defined by claim 45, wherein the spool is formed
of phenolic material.
49. The method as defined by claim 45, wherein the attachment slot
formed across each of the outermost sides of the first and second
outer pole pieces proximate their respective distal ends has a
T-shaped cross section.
50. The method as defined by claim 45, wherein the coil of wire
disposed around the insulating spool has a first end and a second
end, a first lead extending from the first end of the coil, a
second lead being routed from the second end of the coil, between
the coil and the spool, to emerge at the first end of the coil, the
second lead being held in position against the spool by the coil
without requiring additional security.
51. The method as defined by claim 45, further comprising the step
of disposing an insulating cap on the stator pole proximate the top
portion thereof to receive the at least two terminals, thereby
maintaining the terminals in position while the insulating cover is
being molded around the solenoid stator assembly.
52. The method as defined by claim 51, wherein the insulating cap
is formed of phenolic material.
53. The method as defined by claim 45, further comprising the step
of providing the insulating spool with an end flange that extends
from the first outer pole piece to the second outer pole piece
proximate their respective distal ends,
the portion of the end flange disposed between the first and second
outer pole pieces having a dimension that exceeds, by a specific
amount, the distance between the first and second outer pole pieces
when the first and second outer pole pieces are unbiased,
wherein the step of applying a permanent spreading force to the
first and second outer pole pieces to prestress them includes
inserting the end flange into position to apply a force proximate
the distal end of the first outer pole piece and a force proximate
the distal end of the second outer pole piece, the forces acting in
generally coincident but opposite directions to bias the first and
second outer pole pieces away from the central pole piece and
prestress the first and second outer pole pieces with restorative
forces to oppose additional, parallel forces applied to the first
and second outer pole pieces and inhibit additional displacement
caused thereby.
54. The method as defined by claim 53, wherein each of the faces of
the first and second outer pole pieces has a locating ridge
extending along a margin adjacent to the central pole piece to
facilitate the step of positioning the stator core in a mold, the
locating ridge having an edge adjacent to the central pole piece,
the edge being chamfered to facilitate inserting the end flange of
the spool between the first and second outer pole pieces.
55. The method defined by claim 54, further including the step of
removing the locating ridge after the insulating cover is
molded.
56. A system for producing a solenoid stator assembly having an
E-shaped stator pole including a top portion having a first end and
a second end, a first outer pole piece extending substantially
orthogonally from the first end of the top portion, a second outer
pole piece extending from the second end of the top portion in a
direction substantially parallel to that of the first outer pole
piece, and a central pole piece extending from a region of the top
portion located central to the first and second outer pole pieces
and in a direction substantially parallel to those of the first and
second outer pole pieces, the first and second outer pole pieces
each having an outermost side and the first and second outer pole
pieces and the central pole piece each having a distal end, the
first and second outer pole pieces each having an attachment slot
formed across its outermost side proximate its distal end, the slot
being substantially parallel to the top portion, the system
comprising:
means for disposing a coil of electric wire around an insulating
spool;
means for disposing the insulating spool and coil of wire on the
central pole piece;
means for applying permanent spreading forces to the first and
second outer pole pieces to prestress them;
means for connecting the coil across at least two terminals;
and
means for molding an insulating cover that bonds to at least the
stator pole and that substantially envelopes the solenoid stator
assembly except for portions of the terminals and the faces of the
first and second outer pole pieces and of the central pole
piece.
57. The system as defined by claim 56, wherein the spreading force
applied to the first and second outer pole pieces is in a range of
250 to 750 pounds (1100 to 3350 Newtons).
58. The system as defined by claim 56, wherein the insulating cover
is molded in situ of phenolic material.
59. The system as defined by claim 56, wherein the spool is formed
of phenolic material.
60. The system as defined by claim 56, wherein the attachment slot
formed across each of the outermost sides of the first and second
outer pole pieces proximate their respective distal ends has a
T-shaped cross section.
61. The system as defined by claim 56, wherein the coil of wire
disposed around the insulating spool has a first end and a second
end, a first lead extending from the first end of the coil, a
second lead being routed from the second end of the coil, between
the coil and the spool, to emerge at the first end of the coil, the
second lead being held in position against the spool by the coil
without requiring additional security.
62. The system as defined by claim 56, wherein the means for
applying permanent spreading forces to the first and second outer
pole pieces to prestress them comprises:
a first wedging member disposed between the first outer pole piece
and the central pole piece proximate their respective distal ends;
and
a second wedging member disposed between the second outer pole
piece and the central pole piece proximate their respective distal
ends,
the first and second wedging members having dimensions that exceed,
by specific amounts, respective distances between the first and
second outer pole pieces and the central pole piece when the first
and second outer pole pieces are unbiased, and
the first and second wedging members being inserted into their
respective positions to apply a force proximate the distal end of
the first outer pole piece and a force proximate the distal end of
the second outer pole piece, the forces acting in generally
coincident but opposite directions to bias the first and second
outer pole pieces away from the central pole piece and prestress
the first and second outer pole pieces with restorative forces to
oppose additional, parallel forces applied to the first and second
outer pole pieces and inhibit additional displacement caused
thereby.
63. The system as defined by claim 56, wherein the insulating spool
has an end flange that extends from the first outer pole piece to
the second outer pole piece proximate their respective distal
ends,
the portion of the end flange disposed between the first and second
outer pole pieces having a dimension that exceeds, by a specific
amount, the distance between the first and second outer pole pieces
when the first and second outer pole pieces are unbiased, and
the end flange being inserted into position to apply a force
proximate the distal end of the first outer pole piece and a force
proximate the distal end of the second outer pole piece, the forces
acting in generally coincident but opposite directions to bias the
first and second outer pole pieces away from the central pole piece
and prestress the first and second outer pole pieces with
restorative forces to oppose additional, parallel forces applied to
the first and second outer pole pieces and inhibit additional
displacement caused thereby.
64. The system as defined by claim 63, wherein each of the faces of
the first and second outer pole pieces has a locating ridge
extending along a margin adjacent to the central pole piece to
facilitate positioning the stator core in a mold, the locating
ridge having an edge adjacent to the central pole piece, the edge
being chamfered to facilitate inserting the end flange of the spool
between the first and second outer pole pieces, the locating ridge
being removed during the process of completing the solenoid stator
assembly.
65. The system as defined by claim 56, further comprising means for
receiving the at least two terminals and maintaining the at least
two terminals in position while the insulating cover is being
molded around the solenoid stator assembly.
66. The system as defined by claim 65, wherein the means for
receiving the at least two terminals includes an insulating cap
disposed on the stator pole proximate the top portion thereof to
receive the at least two terminals and to maintain the at least two
terminals in position while the insulating cover is being molded
around the solenoid stator assembly.
67. The system as defined by claim 66, wherein the insulating cap
is formed of phenolic material.
Description
TECHNICAL FIELD
This invention relates to solenoid stator assemblies for
solenoid-actuated fuel injectors, particularly for engines.
BACKGROUND ART
Mechanically actuated fuel injector units have been in use for many
years. Continually increasing demands for improvements in vehicle
performance and fuel economy, however, have escalated the need for
more sophisticated fuel injection systems. Microprocessor
technology has become not only a cost-effective means for meeting
the demands of the present but appears to have the potential for
meeting those of the future.
Associated with the application of microprocessor technology has
been the development of electronically actuated fuel injectors. The
development coincides with the steady increase in the total drive
train reliability provided by the industry to reduce maintenance
cost and regular maintenance frequency. Electronically controlled
fuel injectors have the advantage of being compatible with the
electronically controlled engines used in the general transport
industry and have been adopted by major producers of engines.
A typical mechanically actuated fuel injector has a plunger that is
reciprocatingly driven within a bore, or bushing, by, for example,
a camshaft and rocker arm assembly, to provide injection pressure.
Injection timing and fuel metering are controlled by helices and
ports disposed in the plunger and associated bushing.
In a typical electronically actuated fuel injector, such as shown
in U.S. Pat. No. 4,568,021, assigned to the assignee of the present
invention, injection pressure is provided by a mechanically
operated plunger; but a solenoid is used to actuate a valve to
control injection timing and fuel metering.
It is as a result of the transfer of control of the timing and
metering from mechanical to electronic means that improvements in
fuel injection system operation under microprocessor control have
been feasible. Included among additional advantages of
electronically controlled fuel injectors are fewer moving parts,
less weight, less maintenance as a result of there being fewer
service adjustments required to compensate for mechanical wear, and
less cost.
However, one design area requiring special attention is that of
assuring the integrity of the solenoid stator assembly from any
deleterious effects of it being exposed to the fuel, which is under
exceedingly high pressures, in the order of 2,000 pounds per square
inch. Each interface of the stator core with the phenolic housing
and phenolically enshrouded coil on the center pole piece is
subjected to fuel under high pressure which will work to separate
the assembly at the interface, which may lead to hairline fractures
in the phenolic housing and require its replacement. Applicants'
initial commercially practical design modifications included
providing the outer side of each outer pole piece with a T-shaped
groove such that, when the phenolic housing was molded about the
stator and coil subassembly, the housing was mechanically
interlocked with the stator. This improved the overall durability
of the assembly; but over time the high pressure fuel, primarily at
the remaining pole piece interfaces with the phenolic insulating
material, continued to adversely effect durability.
In part, the problem associated with the accessibility of high
pressure fuel to these interfaces was exacerbated by the process
with which the phenolic insulating material was molded about the
stator and coil subassembly. This process included locating the
stator and coil subassembly within the mold by means of vertically
extending locating pins received within locating holes formed
within a phenolic washer positioned between the pole pieces at the
distal ends thereof. The locating holes provided a flow path by
which the high pressure fuel gained access to the interior
interfaces of the pole pieces, which over time could work a
separation at these interfaces.
Thus, with the known solenoid stator assemblies, the insulating
cover material, which relies solely on the strength of the bond
between it and the stator core, may become separated from the
stator core and show hairline fractures as a result of the fuel
being forced between the stator core and the cover material, due to
portions of the stator core to which the cover material is bonded
being flexed, and due to cavitation erosion associated with fluid
dynamics between a reciprocating armature and the stator core.
In part also, the problem associated with the accessibility of high
pressure fuel to these interfaces and the propagation of hairline
fractures was exacerbated by the material characteristics of the
phenolic used for the housing and coil spool, which were found to
be susceptible to swelling when exposed to methanol fuel
especially, and to a lesser extent, diesel fuel.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate any deleterious
effects of fuel under high pressure on the bonding of an
electrically insulating cover material to the solenoid stator core
of an electronically actuated fuel injector.
It is a further object of the present invention to provide a
solenoid stator assembly which is impervious to fuel at every
interface of insulating material with the stator-coil
subassembly.
It is yet another object of the present invention to provide a
means of locating the stator-coil subassembly within a mold so that
cavities formed between stator core pole pieces are completely
filled with phenolic insulating material.
It is another object of the present invention to provide a solenoid
stator assembly in which the interfaces of phenolic with the
stator-core assembly are not subject to disruptive forces resulting
from fluctuating fuel pressures.
It is a further object of the present invention to prestress the
stator-coil subassembly in such a manner that a preload exist at
every interface of the phenolic insulating material with the
stator-coil subassembly, including the interface across the
mechanical bond at the outside surfaces of the outer pole
pieces.
A further object of the present invention is to provide a solenoid
stator assembly wherein the housing, coil spool and cap are
selected of compatible phenolic material having low swell
characteristics when exposed to any of the various fuels, but
particularly methanol fuel and diesel fuel.
In realizing the aforementioned objects, the solenoid stator
assembly constructed in accordance with the present invention in a
preferred form comprises an E-shaped stator core that includes a
top portion having a first end and a second end. A first outer pole
piece extends substantially orthogonally from the first end of the
top portion, a second outer pole piece extends from the second end
of the top portion in a direction substantially parallel to that of
the first outer pole piece, and a central pole piece extends from a
region of the top portion located central to the first and second
outer pole pieces and in a direction substantially parallel to
those of the first and second outer pole pieces. The first and
second outer pole pieces each have an outermost side; and the first
and second outer pole pieces and the central pole piece each have a
distal end, a face being formed across each distal end. The first
and second outer pole pieces each have an attachment slot formed
across its outermost side proximate its distal end. A coil of
electric wire is disposed around the central pole piece, the wire
having at least first and second ends extending from the coil to
form respective first and second leads. The first and second leads
are electrically connected to the first and second terminals
respectively. An electrical insulating member, or means, separates
the coil from the stator core to prevent electrical contact
therebetween. A molded insulating cover is bonded to at least the
stator core and substantially envelopes the solenoid stator
assembly except for portions of the first and second terminals and
the faces of the first and second outer pole pieces and of the
central pole piece. The cover is molded into the attachment slots
in the first and second outer pole pieces to enhance adherence of
the cover material to the first and second outer pole pieces and to
provide a tortuous path to inhibit the flow of errant fuel.
In the preferred construction of the invention, the outer pole
pieces are prestressed by wedging a flange between them to apply a
force proximate the distal end of the first outer pole piece and a
force proximate the distal end of the second outer pole piece, the
forces acting in generally coincident but opposite directions to
bias the first and second outer pole pieces away from each other.
The prestressing provides the first and second outer pole pieces
with restorative forces to oppose any additional, parallel forces
applied to the first and second outer pole pieces and inhibit
additional displacement caused thereby.
In the preferred construction disclosed, the attachment slot formed
in each of the outer pole pieces has a T-shaped cross section. The
shape of the attachment slot enhances its ability to anchor the
assembly-enclosing insulating cover and simultaneously provides a
formidable barrier to fuel that might otherwise be forced under
pressure between the cover and an outer pole piece, particularly
when preloaded as aforementioned.
In the preferred construction of the invention, a spool is used to
provide electrical insulation between the wires of the coil and the
central pole piece of the stator core. The spool additionally
provides a convenient form upon which the coil is wound, preferably
in three layers, and facilitates positioning the coil on the
central pole piece. Another advantage is gained in the area of
quality control by using the spool. A lead from the top layer of
the coil may be secured by passing it between the coil and the
spool so that the wires of the coil hold the lead against the
spool. With the lead secured in this manner, no tape or shim is
required to prevent the coil from unwinding or to prevent the lead
from electrically contacting another element such as an outer pole
piece; and the interior of the stator-coil subassembly may be
completely filled with phenolic during the molding process.
In the preferred construction, an insulating cap is disposed on the
stator core proximate the top portion thereof. The cap receives the
first and second terminals and maintains them in position while the
insulating cover is being molded around the solenoid stator
assembly.
As disclosed, the outer pole pieces may be prestressed by having a
first wedging member, preferably made of metal, disposed between
the first outer pole piece and the central pole piece proximate
their respective distal ends and a second wedging member disposed
between the second outer pole piece and the central pole piece
proximate their respective distal ends. The first and second
wedging members have dimensions that exceed, by specific amounts,
respective distances between the first and second outer pole pieces
and the central pole piece when the first and second outer pole
pieces are unbiased.
In an alternate construction, the coil is wound on a bobbin
disposed around the central pole piece. The bobbin has a flange at
each of its ends that extends orthogonally toward the first and
second outer pole pieces. In this construction, shims, preferably
made of a plastic material, are forced between the bobbin flanges
and the first and second outer pole pieces, urging them away from
the central pole piece and prestressing them.
In the preferred construction as disclosed, the spool has an end
flange that extends from the first outer pole piece proximate its
distal end to the second outer pole piece proximate its distal end.
The portion of the flange that is disposed between the first and
second outer pole pieces has a dimension that exceeds, by a
specific amount, the associated distance between the first and
second outer pole pieces when the first and second outer pole
pieces are unbiased. When inserted, the flange applies a force
proximate the distal end of the first outer pole piece and a force
proximate the distal end of the second outer pole piece, the forces
acting in generally coincident but opposite directions to bias the
first and second outer pole pieces away from the central pole piece
and prestress the first and second outer pole pieces with
restorative forces to oppose additional, fuel-pressure related,
parallel forces that might be applied to the first and second outer
pole pieces and inhibit additional displacement caused thereby.
In the preferred construction of the invention, each of the faces
of the first and second outer pole pieces has a locating ridge
extending along a margin adjacent to the central pole piece to
facilitate positioning the stator core during a subsequent assembly
process. The locating ridge has an edge adjacent to the central
pole piece, the edge being chamfered to facilitate inserting the
flange of the spool between the first and second outer pole pieces.
The locating ridge is removed, for example, by grinding, during the
process of completing the solenoid stator assembly.
The insulating covers of previously constructed solenoid stator
assemblies did not completely seal the spaces around the pole
pieces, allowing fuel under pressure to gain access to internal
spaces of the solenoid stator assembly. This sometimes resulted in
the insulating cover fracturing. In the preferred construction of
the invention, the insulating cover completely isolates the
internal spaces of the solenoid stator assembly from fuel.
The objects described in the foregoing, and other objects,
features, and advantages of the present invention, are readily
apparent from the following detailed description of the best mode
for carrying out the invention when taken in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view, partially in section, of an
electromechanically actuated fuel injector including the primary
operating elements of a solenoid stator assembly as seen in side
view and constructed in accordance with the present invention;
FIG. 2 is a perspective view of the solenoid stator assembly shown
completely sectioned along the same front-to-back plane as in the
partially sectioned view in FIG. 1;
FIG. 3 is an enlarged side view, partially in section of the
solenoid stator assembly of FIG. 1;
FIG. 4 is a perspective view of the solenoid stator assembly of
FIG. 1 shown without an insulating cover;
FIG. 5 is a view, partially in section, of the solenoid stator
assembly of FIG. 4 shown positioned in a mold prior to receiving an
insulating cover;
FIG. 6 is a view of prestressing wedges constructed in accordance
with an embodiment of the present invention;
FIG. 7 is a perspective view of a spool, partly broken away, that
is constructed in accordance with the present invention and that is
an element of the solenoid stator assembly of FIG. 4;
FIG. 8 is a bottom view of the solenoid stator assembly of FIG.
4;
FIG. 9 is a split, sectional, side view of the stator core of FIG.
4 illustrating the prestressing of the stator core in accordance
with the present invention, and
FIG. 10 is a schematic view that illustrates the steps of producing
the solenoid stator assembly of FIG. 3.
BEST MODE FOR CARRYING OUT THE INVENTION
With reference to FIG. 1 of the drawings, a solenoid stator
assembly, generally indicated by reference numeral 10, is shown as
an effective element of a representative electromechanically
actuated fuel injector, generally indicated by reference numeral
11, mounted in an engine 13. As shown in FIGS. 2 and 3 of the
drawings, the stator assembly 10 has an E-shaped stator core 12
that includes a top portion, generally indicated by reference
numeral 14, having a first end 16 and a second end 18. A first
outer pole piece 20 extends substantially orthogonally from the
first end 16 of the top portion 14, a second outer pole piece 22
extends from the second end 18 of the top portion 14 in a direction
substantially parallel to that of the first outer pole piece 20,
and a central pole piece 24 extends from a region of the top
portion located central to the first and second outer pole pieces,
20 and 22 respectively, and in a direction substantially parallel
to those of the first and second outer pole pieces 20 and 22. In
the preferred construction of the invention, the stator core is
laminated, containing approximately 50 laminae, each being shaped
as shown in FIG. 1 and aligned side to side.
The first and second outer pole pieces 20 and 22 each have an
outermost side 26 and 28 respectively; and the first and second
outer pole pieces 20 and 22 and the central pole piece 24 each have
a distal end, generally indicated by reference numerals 30, 32 and
34 respectively, faces 36, 38 and 40 being formed across respective
distal ends 30, 32 and 34. The first outer pole piece 20 has an
attachment slot 42 formed across its outermost side 26 proximate
its distal end 30 and substantially parallel to the top portion 14
of the stator core 12. The second outer pole piece 22 has an
attachment slot 44 formed in a like manner across its outermost
side 28 proximate its distal end 32.
The attachment slots 42 and 44 may have a number of configurations,
each of which may be produced as part of the initial blanking step
in forming the laminations on a punch press. For example, the
attachment slots 42 and 44 may each be rectangular in cross section
(not shown); and their sides may be at right angles relative to the
outermost sides 26 and 28 of the first and second outer pole pieces
20 and 22 respectively. The attachment slots 42 and 44 may also
each be dovetail-shaped in cross section (not shown).
Alternatively, the sides of the attachment slots 42 and 44 may each
define an acute angle relative to the outermost sides 26 and 28 and
angle toward the top portion 14 of the stator core 12. The
attachment slots 42 and 44 that have dovetail-shaped or angled
cross sections provide, among other advantages, that of offering
substantial resistance, in addition to that offered by chemical
bonding of an insulating cover 60 to the outer pole pieces 20 and
22, to any forces acting to pull the insulating cover 60 away from
the outer pole pieces 20 and 22.
While it should be understood that a variety of configurations can
be used, in the preferred construction, and as best shown in FIG. 4
of the drawings, each of the attachment slots 42 and 44 has a
generally T-shaped cross section. The shape of the attachment slots
42 and 44 enhances their ability to anchor the assembly-enclosing
insulating cover and simultaneously provide formidable barriers to
fuel that might otherwise be forced under pressure between the
insulating cover 60 and the outer pole pieces 20 and 22.
As shown in FIG. 4 of the drawings, a coil, generally indicated by
reference numeral 46, of electric wire 48 is disposed around the
central pole piece 24, the wire 48 having at least first and second
ends extending from the coil 46 to form a respective first lead 50
and second lead 52. The first and second leads 50 and 52
respectively are electrically connected to at least a first
terminal 54 and a second terminal 56. An electrical insulating
member, or means, separates the coil 46 from the stator core 12 to
prevent electrical contact with the central pole piece 24. In one
embodiment of the solenoid stator assembly 10, the insulating
member may be in the form of a spool 62 (shown in FIG. 7 and
hereinafter described) that generally surrounds the central pole
piece 24 and around which the coil 46 is disposed.
With reference again to FIGS. 1, 2 and 3 of the drawings, the
molded insulating cover 60 is bonded to at least the stator core 12
and substantially envelopes the solenoid stator assembly 10 except
for upper portions of the first and second terminals, 54 and 56
(FIG. 4 of the drawings) respectively, and the respective faces 36,
38 and 40 of the first and second outer pole pieces 20 and 22 and
of the central pole piece 24. The cover 60 is molded into the
respective attachment slots 42 and 44 in the first and second outer
pole pieces 20 and 22 to enhance adherence of the cover material to
the first and second outer pole pieces 20 and 22 and to provide a
tortuous path to inhibit the flow of errant fuel.
FIG. 5 of the drawings shows the solenoid stator assembly lo
positioned in a representative mold, generally indicated by
reference numeral 86, prior to having an insulating cover 60 (FIG.
molded thereabout. The mold 86 includes an upper portion 88 and a
base portion 90 that define a mold cavity, generally indicated by
reference numeral 92, therebetween. An inlet, or gate, 94, through
which molten material of which the insulating cover 60 is to be
formed is introduced, is disposed in the upper portion 88 of the
mold 86; and an associated vent 96 is also disposed therein. While
it should be understood that the insulating cover 60 may be formed
of any of a number of moldable, electrically insulating materials,
that used in the preferred construction herein disclosed is a
phenolic having low swell characteristics when exposed to various
fuels, particularly methanol fuel and to a lesser extent diesel
fuel. Rogers Rx 630 phenolic, produced by the Fiberite Company is
particularly useful.
The outer pole pieces 20 and 22 are prestressed by applying a force
proximate the distal end 30 of the first outer pole piece 20 and a
force proximate the distal end 32 of the second outer pole piece
22, the forces acting in generally coincident but opposite
directions to bias the first and second outer pole pieces 20 and 22
away from each other. The prestressing provides the first and
second outer pole pieces 20 and 22 with restorative forces to
oppose any additional, parallel forces applied to the first and
second outer pole pieces 20 and 22 and inhibit additional
displacement caused thereby.
With reference to FIG. 6 of the drawings, the first and second
outer pole pieces 20 and 22 may be prestressed by having a first
wedging member 74 disposed between the first outer pole piece 20
and the central pole piece 24 proximate their respective distal
ends 30 and 34 and a second wedging member 76 disposed between the
second outer pole piece 22 and the central pole piece 24 proximate
their respective distal ends 32 and 34. The first and second
wedging members 74 and 76 have dimensions that exceed, by specific
amounts, respective distances between the first and second outer
pole pieces 20 and 22 and the central pole piece 24 when the first
and second outer pole pieces 20 and 22 are unbiased. While it
should be understood that the amount of prestressing may vary as a
function of solenoid application and that a certain degree of
relaxation or shrinkage of the wedges will occur during the molding
of the insulating cover, the outer pole pieces 20 and 22 of the
preferred construction herein disclosed will have a final prestress
force ranging between 250 and 750 pounds (1100 and 3350 Newtons)
and preferably have a force of 500 pounds (2225 Newtons).
With reference again to FIG. 4, in the preferred construction of
the solenoid stator assembly 10, an insulating spool 62 (shown in
detail in FIG. 7 of the drawings) is used to provide electrical
insulation between the coil 46 and the central pole piece 24 of the
stator core 12. The spool 62 additionally provides a convenient
form upon which the coil 46 may be wound and facilitates
positioning the coil 46 on the central pole piece 24.
The spool 62 has an elongate drum portion 63 from one end of which
orthogonally extends a first end flange 64 and from the other end
of which orthogonally extends a second end flange 66. The first end
flange 64 defines along its peripheral edge a pair of diametrically
opposed notches, generally indicated by reference numeral 68, to
provide respective paths for the first and second leads 50 and 52.
The second end flange 66 defines along its peripheral edge at least
one notch, generally indicated by reference numeral 70, to provide
a path for the second lead 52. The drum portion 63 defines in its
outer surface at least one channel 65 extending from a notch 68 in
the first end flange 64 to notch 70 of the second end flange 66. In
the preferred construction of the spool 62, the notches 68 and 70
in the first and second end flanges 64 and 66 respectively, and the
interconnecting channel 65 will be provided at both sides of the
spool 62 and arranged symmetrically about the peripheral edges
thereof to facilitate assembly. While it should be understood that
the spool 62 may be formed of any of a number of electrically
insulating materials, that used in the preferred construction
herein disclosed is a phenolic having low swell characteristics
when exposed to various fuels, particularly methanol fuel and to a
lesser extent diesel fuel. Fiberite FM 4004 phenolic, as produced
by the Fiberite Company, is particularly useful.
The coil 46 is preferably wound in three layers, the first layer
being started at the end of drum portion 63 of the spool 62 that is
proximate the first end flange 64 thereof, the third layer being
completed at the end of the drum portion 63 that is proximate the
second end flange 66 of the spool 62. The first lead 50 is routed
to the first terminal 54 through a notch 68 in the first end flange
64. The second lead 52 is routed under the coil 46 at the notch 70
in the second end flange 66, along a channel 65 in the drum portion
63 of the spool 62, and through the other notch 68 in the first end
flange 64 to the second terminal 56.
In providing the capability of routing the second lead 52 between
the coil 46 and the spool 62, the latter provides a significant
advantage over devices requiring more conventional lead routing
practices. With the second lead 52 secured beneath the coil in the
manner disclosed, no tape or other fastening device is required to
prevent the coil 46 from unwinding or to prevent the second lead 52
from contacting another element such as a first or second outer
pole piece 20 or 22.
An insulating cap 72 is disposed on the stator core 12 proximate
the top portion 14 thereof. The cap 72 is formed with recesses to
receive the first and second terminals 54 and 56 and maintains them
in position while the insulating cover 60 is being molded around
the solenoid stator assembly 10. Portions of the insulating cap 72
overlap associated portions of the spool 62 to provide an
insulating barrier between the first and second leads 50 and 52
respectively and the stator core 12. While it should be understood
that the insulating cap 72 may be formed of any of a number of
electrically insulating materials, that used in the preferred
construction herein disclosed is a phenolic having low swell
characteristics, preferably the same phenolic as used for the spool
62, to provide complete compatibility during the molding of the
housing 60.
The second end flange 66 of the spool 62 extends from the first
outer pole piece 20 proximate its distal end 30 to the second outer
pole piece 22 proximate its distal end 32. The portion of the
second end flange 66 that is disposed between the first outer pole
piece 20 and second outer pole piece 22 has a dimension that
exceeds, by a specific amount, the associated distance between the
first and second outer pole pieces 20 and 22 when the first and
second outer pole pieces 20 and 22 are unbiased. This is shown in
detail in FIGS. 8 and 9. When inserted, the second end flange 66
applies a force proximate the distal end 30 of the first outer pole
piece 20 and a force proximate the distal end 32 of the second
outer pole piece 22, the forces acting in generally coincident but
opposite directions to bias the first and second outer pole pieces
20 and 22 away from the central pole piece 24 and prestress the
first and second outer pole pieces 20 and 22 with restorative
forces to oppose any additional, parallel forces that might be
applied to the first and second outer pole pieces 20 and 22 and
inhibit additional displacement caused thereby.
Side (a) of FIG. 9 shows the stator core 12 before the spool 62 is
fully inserted onto the central pole piece 24 thereof. As shown,
the second end flange 66 of the spool 62 extends a specific
distance d beyond the inner surface of the first outer pole piece
20. Side (b) of FIG. 9 shows the stator core 12 after the spool 62
has been fully inserted. As shown, the second end flange 66 has
displaced the second outer pole piece 22 away from the central pole
piece 24 by an angle .alpha.. It is as a result of the displacing
action of the second end flange 66 that the first and second outer
pole pieces 20 and 22 are prestressed. To facilitate positioning
the second end flanges 66 between the first and second outer pole
pieces 20 and 22, the distal ends 30 and 32 respectively thereof
may be spread using the T-shaped slots 42 and 44 disposed therein
to anchor force-applying members (not shown).
Each of the faces 36 and 38 of the first and second outer pole
pieces 20 and 22 has a respective locating ridge 80 and 82
extending along a margin adjacent to the central pole piece 24 to
facilitate positioning the stator core 12 during a subsequent
assembly process. Each locating ridge 80 and 82 has an edge 84
adjacent to the central pole piece 24, the edge 84 being chamfered
to facilitate inserting the second end flange 66 of the spool 62
between the first and second outer pole pieces 20 and 22. The
locating ridges 80 and 82 are removed, for example, by grinding,
during the process of completing the solenoid stator assembly
10.
It should be understood that practical features, such as sleeves
passing through the insulating cover 60, may be included to provide
holes 98 (FIG. 2) through which mounting screws 100 (FIG. 1) may be
disposed to secure the solenoid stator assembly 10 to an
electromechanically actuated fuel injector 11.
The method for producing a preferred embodiment of the solenoid
stator assembly can best be understood with reference to the steps
outlined in FIG. 10 of the drawings in conjunction with previously
described FIGS. 4 through 9. A coil 46 of electric wire 48 is
disposed around the insulating spool 62. The coil 46 is preferably
wound in three layers. The first layer is started at the end of the
drum portion 63 of the spool 62 that is proximate the first end
flange 64 thereof, and the third layer is completed at the end of
the drum portion 63 that is proximate the second end flange 66 of
the spool 62. The spool 62 is slid, with the first end flange 64
leading, onto the central pole piece 24 of the stator core 12 until
the second end flange 66 contacts the locating ridges 80 and 82 on
the first and second outer pole pieces 20 and 22 respectively.
The distal ends 30 and 32 of the first and second outer pole pieces
20 and 22 respectively may be spread, using the T-shaped slots 42
and 44 disposed therein to anchor force-applying members (not
shown), to facilitate passing the second end flange 66 between the
first and second pole pieces 20 and 22. The chamfered edges 84 of
the locating ridges 80 and 82 also facilitate inserting the second
end flange 66 into position.
With the spool 62 in place on the central pole piece 24, the
insulating cap 72 is disposed on the stator core 12 proximate the
top portion 14 thereof. The first and second leads 50 and 52 are
electrically connected to the first and second terminals 54 and 56
respectively, and the first and second terminals 54 and 56 are
disposed in the recesses formed in the insulating cap 72. The first
lead 50 is routed to the first terminal 54 through a notch 68 in
the first end flange 64. The second lead 52 is routed under the
coil 46 at the notch 70 in the second end flange 66, along the
channel 65 in the drum portion 63 of the spool 62, and through
another notch 68 in the first end flange 64 to the second terminal
56.
After the stator core 12, spool 62, coil 46, insulating cap 72 and
terminals 54 and 56 have been assembled as described, they are
placed in the mold 86 as represented in FIG. 5. The assembly 10 is
positioned on the base portion 90 of the mold 86 so that the
locating ridges 80 and 82 are disposed in associated recesses
formed in the base portion 90 of the mold 86. The upper portion 88
of the mold 86 is then disposed atop the base portion 90 thereof,
forming a mold cavity 92 around the assembly 10. Molten insulating
material, which, in the preferred construction of the invention, is
phenolic, is introduced to the mold 86 through the inlet, or gate,
94 to form an insulating cover 60 (FIGS. 1 through 3), gasses
produced during the molding operation being exhausted from the mold
cavity 92 through the associated vent 96 in the upper portion 88 of
the mold 86.
The insulating material is bonded to at least the stator core 12
and substantially envelopes the solenoid stator assembly 10 except
for portions of the first and second terminals 54 and 56, the faces
36 and 38 of the first and second outer pole pieces 20 and 22
respectively and the face 40 of the central pole piece 24. When the
insulating cover 60 has set sufficiently, the upper portion 88 of
the mold 86 is separated from the base portion 90 thereof; and the
solenoid stator assembly 10 is removed from the mold 86. The
locating ridges 80 and 82 are removed from their respective first
and second outer pole pieces 20 and 22 by a machining process such
as grinding.
While the best mode for carrying out the invention has been
described in detail, those familiar with the art will recognize
various alternative designs and embodiments as being part of the
invention. For example, while the foregoing has been limited to
describing the invention as applied to a solenoid stator assembly
having an E-shaped stator core, one skilled in the art will
recognize its application to a solenoid stator assembly having a
C-shaped stator. Thus it is intended that the invention be
recognized as defined by the following claims.
* * * * *